Micronote 130 - Overall TVS Selection (149.43 kB)

OVERALL SELECTION OF TRANSIENT VOLTAGE
SUPPRESSOR PART NUMBERS FOR RTCA/DO-160
Previous Microsemi MicroNotes 104, 125 and 127 have described how to calculate and
select Transient Voltage Suppressor (TVS) devices when knowing the waveform, the
source impedance (ZS), and the open-circuit voltage (VOC) of the transient. This also
involved considerations of different Peak Pulse Power (PPP) capabilities for various pulse
widths beyond those specifically rated in TVS data sheets (such as 10/1000 μs). Further
methods will now be demonstrated to calculate and summarize in two convenient tables
all Microsemi TVS part numbers compliant to the RTCA/DO-160E (or D) specification
for “Environmental Conditions and Test Procedures for Airborne Equipment.”
One of the fundamental relations in selecting the TVS is identifying the resulting surge
or pulse current (IP) with the above features. This has previously been shown as:
IP = (VOC – VC)/ ZS
With this example, we can also determine the resulting PPP by multiplying the IP value
by the VC. For this worst-case calculation, the VC is considered the maximum value
shown on the TVS data sheets and IP becomes the Peak Pulse Current (IPP) at the pulse
width and waveform of interest. We then have:
(VC)(IPP) = PPP = VC(VOC – VC)/ ZS
EQ 1
Placing emphasis on the power instead of current simplifies matters when gaining
insight to various TVS products with specific PPP ratings. It also gives opportunity to
examine a large number of products and what specifications may be met that have also
provided information on VOC and ZS for defining the transient pulse. In this analysis, the
PPP is the value determined for the TVS at the desired waveform and pulse duration after
a conversion is made from the original data sheet ratings (such as 10/1000 μs). These
methods for conversion are also described in MicroNotes 104, 120, and 127. When using
the appropriate PPP values, we can then solve for VC and what values comply with the
needed PPP after these conversions are made.
When rearranging terms in EQ 1, we have:
ZSPPP = VCVOC – VC2
or,
VC2 – VOCVC + ZSPPP = 0
This is in a format for easily solving VC using the Quadratic Equation. When using that
method, we have:
VC = 0.5(VOC) ± 0.5(VOC2 – 4ZSPPP)1/2
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EQ 2
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This calculation for VC provides a relatively easy method to recognize what Clamping
Voltages are required for each of the popular TVS ratings to comply with various
industry specifications such as the RTCA/DO-160E for aircraft lightning. For example,
we can use the RTCA/DO-160E, Section 22, and Table 22-2 therein concerning “Test
Levels for Pin Injection” and its described ZS and VOC values to determine what Vc
values will comply using EQ 2 for various power ratings of TVSs after converting the PPP
to the desired Waveform. For Waveform 4 (6.4/69 μs as shown in Figure 1), MicroNote
127 describes a PPP conversion factor of 3.33 from the longer duration 10/1000 μs rating
used in the industry. This conversion factor includes an added 20% worst-case condition
in duration (6.4/83 μs) as also required in the RTCA/DO-160E specification for
“Environmental Conditions and Test Procedures for Airborne Equipment.”
RTCA/DO-160 Voltage Waveform 4
FIGURE 1
If we initially use an example TVS in the industry rated at 500 W at 10/1000 μs, this
equates to a PPP level of 3.33 x 500 = 1665 W for the described Waveform 4. When also
using the VOC and ZS values for Waveform 4 from Table 22-2 of RTCA/DO-160D, we
can solve EQ 2 for VC. For all five Levels of Waveform 4, the generator source
impedance is 5 Ohms (VOC/ISC). Starting with Level 1 or Level 2 conditions with their
low VOC values and substituting into EQ 2, we find that the roots of the equation are both
imaginary numbers since there is a square root of a negative value. This indicates the
VOC for Level 1 and 2 are comparatively low (50 V and 125 V respectively) relative to
the product of source impedance ZS and Peak Pulse Power PPP in the square root portion
of EQ 2. However this is not the case for Level 3 or higher where the calculation gets
more interesting. Level 3 specifies a VOC of 300 V. Substituting the VOC value of 300 V
from Table 22-2 with the ZS of 5 Ohms as well as the earlier determined PPP value of
1665 W as the equivalent capability for the shorter Waveform 4 into EQ 2, we have the
following:
VC = 0.5(300) ± 0.5[3002 – 4(5)(1665)]1/2
VC = 150 ± 0.5(90,000 – 33,300)1/2 = 150 ± 119
Therefore:
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VC = 31.0 V and VC = 269 V
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When further comparing these VC values with EQ 1, the PPP will be less than or equal
to 1665 W at 6.4/83 μs (500 W at 10/1000 μs) when VC 31.0 V or VC 269 V. As a
result, the TVS device will also meet the requirements of the DO-160D specification for
Pin Injection tests of Waveform 4 at Level 3 conditions at 25ºC when the VC is in these
lower or higher specified ranges. If the 500 W series of TVSs does not have the higher
voltage devices included in that series where VC 269 V, only the lower voltage device
part numbers will comply where VC 31.0. For example in the 500 W rated TVSs of the
SMAJ5.0A thru SMAJ170A (or CA) series, only the SMAJ5.0A thru SMAJ18A (or CA)
may be used for Waveform 4, Level 3 after comparing the maximum Clamping Voltage
VC values specified in the data sheet for each device in this particular series.
A similar analysis for the more severe Level 4 with a higher VOC of 750 V would reveal
the clamping voltages must be VC 11.3 V or VC 738.7 V. This only allows the lowest
TVS part numbers in the 500 W SMAJxxx series to be used such as the SMAJ5.0A,
SMAJ6.0A, and SMAJ6.5A (or CA). The very high clamping voltage devices above
738.7 V have virtually no practical application and do not exist in this TVS series.
A further similar analysis for the next higher Level 5 of Waveform 4 would reveal that
no devices in the standard 500 W rated TVS products at 10/1000 μs would comply with
that test level threat. As a result, higher PPP ratings for TVSs must be used.
The same calculations can be made for other popular TVS devices from Microsemi
with PPP ratings up to 200,000 W. These are all summarized in the Tables shown herein
for the important Waveforms and threat Levels in the RTCA/DO-160E specification
including Waveform 5A (40/120 μs as shown in Figure 2) that is much more severe with
its longer duration and lower source impedance.
RTCA/DO-160 Voltage Waveform 5A
FIGURE 2
Although three Waveforms are specified in Table 22-2 of the RTCA/DO-160E
specification (Waveforms 3, 4 and 5A), it has been demonstrated in MicroNote 127 that
any TVS that complies with the frequently specified Waveform 4 will also easily comply
with the shorter Waveform 3. The Waveform 3 calculations are therefore not shown. All
the TVS part numbers relative to their VC calculation in EQ 2 have been determined and
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listed for compliance at 25ºC to the worst-case conditions of Waveform 4 and Waveform
5A in Table 1 and Table 2 respectively for all five threat Levels identified in the
RTCA/DO-160E specification. For higher temperature deratings, see MicroNote 132.
PPP @10/1000 μs
(or as specified)
Table 1. WAVEFORM 4 Clamping Voltage (VC) and Microsemi
TVS Part Numbers Compliant to RTCA/DO-160E @ 25°C
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
1
2
3
4
5
All
All
SMAJ5.0A-170A,CA SMAJ5.0A-170A,CA
P5KE5.0A-170A,CA P5KE5.0A-170A,CA
1N6103A-6137A
1N6103A-6137A
1N6461-1N6468
1N6461-1N6468
HSMBJSAC5.0-50
HSMBJSAC5.0-50
SAC5.0-50
SAC5.0-50
All
All
SMBJ5.0A-170A,CA
SMBJ5.0A-170A,CA
P6KE6.8A-200A,CA
P6KE6.8A-200A,CA
All
All
SMCJ5.0A-170A,CA SMCJ5.0A-170A,CA
1.5KE6.8A-400A,CA 1.5KE6.8A-400A,CA
1N5629A-1N5665A
1N5629A-1N5665A
1N5907, 1N5908
1N5907, 1N5908
1N6036A-1N6072A
1N6036A-1N6072A
1N6138A-1N6173A
1N6138A-1N6173A
1N6267A-1N6303A
1N6267A-1N6303A
1N6469-1N6476
1N6469-1N6476
LC6.5-170A
LC6.5-170A
LCE6.5-170A
LCE6.5-170A
SMCJLCE6.5-170A
SMCJLCE6.5-170A
All
All
SMLJ5.0A-170A,CA
SMLJ5.0A-170A,CA
All
All
5KP5.0A-110A,CA
5KP5.0A-110A,CA
All
All
15KP17A-280A,CA
15KP17A-280A,CA
500 W
600 W
1500 W
3000 W
5000 W
15,000 W
VC 31.0 V
SMAJ5.0A-18A,CA
P5KE5.0A-18A,CA
1N6103A-6114A
1N6461-1N6464
HSMBJSAC5.0-15
SAC5.0-15
VC 38.2 V
SMBJ5.0A-22A,CA
P6KE6.8A-27A,CA
All
SMCJ5.0A-170A,CA
1.5KE6.8A-400A,CA
1N5629A-1N5665A
1N5907, 1N5908
1N6036A-1N6072A
1N6138A-1N6173A
1N6267A-1N6303A
1N6469-1N6476
LC6.5-170A
LCE6.5-170A
SMCJLCE6.5-170A
All
SMLJ5.0A-170A,CA
All
5KP5.0A-110A,CA
All
15KP17A-280A,CA
VC 11.3 V
SMAJ5.0-6.5A,CA
P5KE5.0-6.5A,CA
1N6103A
1N6461-1N6462
None
VC 13.6 V
SMBJ5.0-8.0A,CA
P6KE6.8A-9.1A,CA
VC 35.0 V
SMCJ5.0A-20A,CA
1.5KE6.8A-24A,CA
1N5629A-1N5642A
1N5907, 1N5908
1N6036A-1N6048A
1N6138A-1N6151A
1N6267A-1N6280A
1N6469-1N6472
LC6.5-20A
LCE6.5-20A
SMCJLCE6.5-20A
VC 74.0 V
SMLJ5.0A-45A,CA
VC 135.5 V
5KP5.0A-78A,CA
All
15KP17A-280A,CA
None
PLAD15KP5.0-400A,CA PLAD15KP5.0-400A,CA PLAD15KP5.0-400A,CA PLAD15KP5.0-400A,CA
All
30KPA28A-288A,CA
30,000 W
All
30KPA28A-288A,CA
All
30KPA28A-288A,CA
VC 16.0 V
SMCJ5.0A-8.0A,CA
1.5KE6.8A-11A,CA
1N5629A-1N5634A
1N5907, 1N5908
1N6036A-1N6040A
1N6138A-1N6143A
1N6267-1N6272A
1N6469-1N6470
LC6.5-9.0A
LCE6.5-9.0A
SMCJLCE6.5-9.0A
VC 32.0 V
SMLJ5.0A-18A,CA
VC 54.0 V
5KP5.0A-33A,CA
VC 175.5 V
15KP17A-100A,CA
PLAD15KP5.0-100A,CA
All
30KPA28A-288A,CA
VC 426 V
30KP33A-260A,CA
PLAD30KP10-400A,CA* PLAD30KP10-400A,CA* PLAD30KP10-400A,CA* PLAD30KP10-400A,CA* PLAD30KP10-260A,CA*
65,000 W
@ 6.4/69 μs
100,000 W
@ 6.4/69 μs
130,000 W
@ 6.4/69 μs
All
RT65KP48-75A,CA
All
RT65KP48-75A,CA
All
RT65KP48-75A,CA
All
RT65KP48-75A,CA
All
RT65KP48-75A,CA
All
All
All
All
RT100KP40-400A,CA RT100KP40-400A,CA RT100KP40-400A,CA RT100KP40-400A,CA
VC 426 V
RT100KP40-200A,CA
All
All
All
All
All
RT130KP275-295CA, RT130KP275-295CA, RT130KP275-295CA, RT130KP275-295CA, RT130KP275-295CA,
RT130KP275-295CV** RT130KP275-295CV** RT130KP275-295CV** RT130KP275-295CV** RT130KP275-295CV**
1. The CA suffix signifies Bidirectional TVS options where shown.
2. Part numbers with prefix SMBJ, SMCJ, or SMLJ are also available as SMBG, SMCG, or
SMLG prefix respectively for Gull-wing termination options rather than the J-bend shown.
3. Compliant capabilities include a worst-case +20% tolerance for waveform durations in RTCA/DO-160E.
* PLAD15KPxxx and PLAD30KPxxx series have lower thermal resistance to minimize cumulative heating on multiple surges.
** CV suffix signifies lower clamping voltage compared to the CA suffix.
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Table 2. WAVEFORM 5A Clamping Voltage (VC) and Microsemi
TVS Part Numbers Compliant to RTCA/DO-160E @ 25°C
PPP @10/1000 μs
(or as specified)
500 W
600 W
LEVEL
1
LEVEL
2
LEVEL
3
LEVEL
4
LEVEL
5
All
VC 10.1 V
None
None
None
SMAJ5.0A-170A,CA
P5KE5.0A-170A,CA
1N6103A-6137A
1N6461-1N6468
HSMBJSAC5.0-50
SAC5.0-50
SMAJ5.0A,CA
P5KE5.0A,CA
None
None
None
VC 12.1 V
None
None
None
VC 114.9 V **
SMAJ78A-170A,CA
P5KE78A-170A,CA
1N6130A-6137A
All
VC 12.4 V
SMBJ5.0A-170A,CA
P6KE6.8A-200A,CA
SMBJ5.0A-7.0A,CA
P6KE6.8A-8.2A,CA
VC 112.6 V **
SMBJ75A-170A,CA
P6KE91A-200A,CA
1500 W
All
VC 42.2 V
SMCJ5.0A-170A,CA
1.5KE6.8A-400A,CA
1N5629A-1N5665A
1N5907, 1N5908
1N6036A-1N6072A
1N6138A-1N6173A
1N6267A-1N6303A
1N6469-1N6476
LC(E)6.5-170A
SMCJLCE6.5-170A
SMCJ5.0A-26A,CA
1.5KE6.8A-30A,CA
1N5629-1N5644A
1N5907, 1N5908
1N6036A-1N6050A
1N6138A-1N6153A
1N6267A-1N6282A
1N6469-1N6473
LC(E)6.5-26A
SMCJLCE6.5-26A
SMCJ5.0A-7.0A,CA
1.5KE6.8A-8.2A,CA
1N5629-1N5631A
1N5907, 1N5908
1N6036A-1N6037A
1N6138A-1N6140A
11N6267A-1N6269A
1N6469-1N6470
LC(E)6.5-7.0A
SMCJLCE6.5-7.0A
VC 82.8 V **
SMCJ58A-170A,CA
1.5KE68A-400A,CA
1N5653A-1N5665A
1N6059A-1N6072A
1N6162A-1N6173A
1N6291A-1N6303A
LC(E)58A-170A
SMCJLCE58A-170A
3000 W
5000 W
15,000 W
30,000 W
65,000 W
@ 6.4/69 μs
100,000 W
@ 6.4/69 μs
130,000 W
@ 6.4/69 μs
All
All
VC 25.5 V
VC 9.4 V
SMLJ5.0A-170A,CA
SMLJ5.0A-170A,CA
SMLJ5.0A-15A,CA
SMLJ5.0A,CA
All
All
VC 45.8 V
VC 15.9 V
5KP5.0A-110A,CA
5KP5.0A-110A,CA
5KP5.0A-28A,CA
5KP5.0A-8.0A,CA
All
All
All
15KP17A-280A,CA
15KP17A-280A,CA
15KP17A-280A,CA
PLAD15KP5.0-400A,CA* PLAD15KP5.0-400A,CA* PLAD15KP5.0-400A,CA*
All
All
All
30KPA28A-400A,CA
30KPA28A-400A,CA
30KPA28A-400A,CA
PLAD30KP10-400A,CA* PLAD30KP10-400A,CA* PLAD30KP10-400A,CA*
All
All
All
RT65KP48-75A,CA
RT65KP48-75A,CA
RT65KP48-75A,CA
None
VC 49.9 V
VC 22.2 V
15KP17A-28A,CA
PLAD15KP5.0-28A,CA*
PLAD15KP5.0-13A,CA*
VC 109.1 V
VC 45.0 V
30KPA28A-64A,CA
PLAD30KP10-64A,CA*
PLAD30KP10-26A,CA*
None
None
None
All
All
All
VC 109.1 V
RT100KP40-400A,CA
RT100KP40-400A,CA
RT100KP40-400A,CA
RT100KP40-54A,CA
All
All
All
None
None
RT130KP275-295CA or RT130KP275-295CA or RT130KP275-295CA or
RT130KP275-295CV*** RT130KP275-295CV*** RT130KP275-295CV***
1. The CA suffix signifies Bidirectional TVS options where shown.
2. Part numbers with prefix SMBJ, SMCJ, or SMLJ are also available as SMBG, SMCG, or
SMLG prefix respectively for Gull-wing termination options rather than the J-bend shown.
3. Where no generic standard part is available (none indicated), consult factory for custom options.
4. Compliant capabilities include a worst-case +20% tolerance for waveform durations in RTCA/DO-160E.
* PLAD15KPxxx and PLAD30KPxxx series have lower thermal resistance to minimize cumulative heating on multiple surges.
** Part numbers are guard banded one higher value to ensure VC than value shown.
*** CV suffix signifies lower clamping voltage compared to the CA suffix.
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o
TL (Lead) or TC (Case) Temperature C
Derating Curve (Plastic Packages)
FIGURE 3
Peak Pulse Power (PPP) or continuous
o
Power in Percent of 25 C Rating
Peak Pulse Power (PPP) or continuous
o
Power in Percent of 25 C Rating
If higher ambient temperatures are used well beyond the PPP ratings at 25ºC, the product
selections in Tables 1 and 2 will be more limited as shown in MicroNote 132. For random
recurring transient events where a TVS device recovers to ambient temperatures before the next
transient, the Ppp capability at 25ºC will linearly decline to 50% at 150ºC as shown in Figure 3
below. This linear derating will stop and abruptly become zero thereafter above 150ºC if they
are plastic packages. They can also further derate linearly to 175ºC (or 200ºC) if they are glass,
ceramic or metal packages as determined by the applicable package material properties and
overall ratings in storage and operating temperatures further shown in Figure 4 below.
Most applications are at ambient temperatures well below 150ºC. An operating temperature of
70ºC for TVS devices would derate by 18% from their maximum rating at 25ºC. This would
also apply to Waveform 4 or 5A transients that are considered “Single Stroke” for Pin Injection
test levels in Table 22-2 of RTCA/DO-160E. Further details of selecting devices at various
elevated temperatures are shown in MicroNote 132 in “DIRECTselect” Graphs 1 thru 14. The
various temperature characterizations in those graphs also show the same selection results at
25ºC in Tables 1 and 2 herein for Microsemi TVS products.
o
TL (Lead) or TC (Case) Temperature C
Derating Curve (Glass/Metal/Ceramic Packages)
FIGURE 4
A more severe linear slope derating to zero at 150ºC or 175ºC (or 200ºC) is applicable for
longer average power considerations such as when a TVS might also be used as a Zener Voltage
Regulator with continuous or dc power. In those examples, the “average power” derating
method becomes applicable as further shown separately in Figures 3 and 4. As a result, there is
an important distinction in “random recurring” transients for PPP (duty factors of 0.01% or less)
compared to average long-term power derating considerations. In some applications where
“multiple stroke” or “multiple burst” surge requirements exist and higher duty factors generate
cumulative heating effects, further considerations must be given to minimize those effects. This
includes using TVS designs with very low thermal resistance junction to ambient with good heat
sinking as may be obtained with the new PLAD15KPxxx and PLAD30KPxxx series products
shown in Tables 1 and 2. This will ensure minimum case temperatures (TC) for these type
packages as shown in Figures 3 and 4 above. It will also permit greater PPP performance with the
described longer “multiple strokes” or “bursts” identified in the RTCA/DO-160 specification.
If the application only involves relatively low current demands for the protected load, external
resistance can also be added to the source impedance ZS thus reducing the incident surge current
level on a TVS protecting that load. This is also described in the first page equations as well as
in MicroNote 125 and MicroNote 127. This will effectively reduce the PPP requirements of the
TVS and expand the possible selection of VC and part numbers provided in Tables 1 and 2.
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In addition to these standard TVS product part numbers, Microsemi also provides options for
additional screening where higher reliability testing may be required. For flight hardware,
Microsemi offers Avionics Grade component screening, available by adding an MA™ prefix to
the standard part number. This screening is performed on 100% of the production units that
includes additional surge tests, temperature cycling, and high temperature reverse bias (HTRB)
screening. For applications where a militarized device is required and no qualified part exists in
accordance with MIL-PRF-19500, Microsemi offers equivalent JAN, JANTX, JANTXV, and
JANS screening by adding MQ, MX, MV, or MSP prefixes respectively to standard part
numbers. This also includes specific options for various low capacitance TVS devices as shown
in Tables 1 and 2 herein. Also see MicroNote 129 (Table II) for further details on up-screening
where some differences may occur in available options between plastic versus metal or glass
packaging.
In summary, this article has provided a calculation method for Transient Voltage Suppressor
compliance to the five test levels of Waveform 4 and 5A for pin injection in the RTCA/DO-160F
specification and many of its earlier revisions. The results of those calculations are summarized
in the tables herein as an overview for providing a quick selection of TVS device part numbers.
These same results are also reflected in MicroNote 132 in the “DIRECTselect” Graphs 1 thru 14
at 25°C as well as for various elevated temperatures.
For other smaller TVS components primarily intended for ESD protection including the
Microsemi TVSarrays™, consult the Microsemi Scottsdale Division for further information.
For additional technical assistance and information, contact Kent Walters
(kwalters@microsemi.com).
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